Inflatable packers are used in the oil industry to bridge a well bore or to isolate a zone therein. A typical inflatable packer has a tubular mandrel or body that carries an elongated inner elastomeric sleeve which is surrounded by a layer of protective armor such as overlapped slats, reverse-layed cables, or woven composite constructions including cables or wires in an elastomer matrix. An outer elastomer seal sleeve surrounds all or a portion of the armor layer, so that when fluid under pressure is supplied to the inside of the inner elastomer sleeve member, this sleeve member, the armor layer and the outer elastomer seal sleeve are expanded. The outer sleeve engages the well bore wall to provide a pack-off, and any uncovered portion of the armor also engages the well bore wall to provide additional frictional resistance to longitudinal movement.
The opposite end portions of the armor layer and the inner elastomer sleeve are surrounded by stress rings which are the principle :radial load-bearing members of the end fittings which attach these elements to the mandrel. Such stress rings often are the limiting factors in terms of maximum pressure differentials to which the inflatable packer assembly can be subjected. If a stress ring cracks and fails downhole, the packer assembly also is likely to rupture and fail also. Moreover, a stress ring may be permanently deformed to the extent that the packer cannot be retrieved from the well through production tubing through which the packer was initially run into the well.
A general object of the present invention is to provide an inflatable packer apparatus having new and improved stress rings which enable the packer element to be inflated to higher pressure differentials without damage to the stress rings at the opposite end thereof.